Decorative constructional materials based on relatively light, synthetic stone with a certain translucency are already well-known. They are largely particulate composite systems with a binder based on the principle of low-colour, clear reactive resin with a larger content of powder filler and other additional substances relieving technology, modifying properties, and influencing processing, etc. Translucent reactive polyester resin is an example of the binder used. Powdery calcium carbonate, silica powder, aluminium hydroxide (also known as ATH, alumina trihydrate, aluminium trihydroxide, hydrated alumina) plaster, marble, etc. are examples of fillers used. Peroxides such as MEKP are generally used as initiators. Actual production takes place by introducing a reactive mixture into a mould and subsequently removing it from the mould after sufficient hardening, and then carrying out the necessary mechanical treatment. These products are described in the U.S. Pat. Nos. 3,396,067; 3,488,246; 3,642,975; 3,847,865 and 4,107,135. Synthetic stone described in the above-mentioned patents has good mechanical and visual properties. However, it is not very translucent, and this is quickly worsened by damage to its surface caused easily by scratching, e.g. mechanical abrasion during handling.
A somewhat better translucency and appearance, as well as more suitable behaviour is displayed by products with a limited amount of pigments and with surface protection provided by a so-called “gel coat”, for example based on unfilled iso-neopenthylglycolic polyester. These types of synthetic stone are products with a somewhat enhanced translucency and with greater resistance to surface damage, however, not providing a high translucency.
Another improvement to the translucency of this type of product can be achieved using a highly pure pseudo-crystalline filler made of alumina trihydrate, with chemical formula Al2O3×3 H2O (alumina trihydrate), containing Al(OH)3 with a purity of greater than 99% and a refractive index of light of between 1.4 and 1.65 comprising of a mixture of irregular powder particles. This filler is made of agglomerates, mono-crystals, and fine granules with particles less than approx. 70 μm in length, possibly with translucent and/or transparent particles. In particular using resin based on acrylate modified polyesters and also primarily using acrylate reactive resins with a refractive index of light approaching the refractive index of the alumina trihydrate used, according to U.S. Pat. No. 4,159,301. These products are somewhat more translucent. They have a better surface and extraordinarily high resistance to surface damage, which results in a reduction in translucency. Products of this type often referred to as “solid surface” achieve a certain three-dimensional projection of space-depth, as a result of their optically more suitable components, but there is only a partial increase in their translucency.
U.S. Pat. No. 5,286,290 describes the use of a coloured alumina trihydrate without the use of pigments which reduce translucency. Not even this leads to a significant improvement in translucency. U.S. Pat. Nos. 4,085,246; 4,159,307 and 5,304,592 describe the use of hollow and later full, translucent partial substitutes of the filler used, e.g. using so-called glass “microspheres, micropearls”, particles such as polypropylene, polyethylene, HD-polyethylene, etc. Their use actually leads to a targeted reduction in specific weight and to an increase in resistance to thermal shock, but there is no significant increase in translucency. Constructional, decorative materials of this type labelled as synthetic stone “cultured marble”, or “cultured onyx” displays very good mechanical properties, a nice natural appearance and are pleasant to touch. However, light only passes through them to a very limited extent. The translucency of such materials, measured on 6 mm thick test plates with light shining on them from one side, is very low and generally of the order deeply under of 4 to 5%.
The submitted invention proposes to eliminate the deficiencies mentioned above and create a synthetic stone with high translucency.